In conjunction with Holevo's theorem [1]}, [2]}, we have
\(I({\small (a,s)} : o) &\le S\left(\frac{1}{2 (4^n - 1)} \sum _{a,s} \rho _{(a,s)}^{\otimes N}\right) - \frac{1}{2 (4^n - 1)} \sum _{a,s} S\left(\rho _{(a,s)}^{\otimes N}\right)\\&\le N n \log (2) - \frac{1}{2 (4^n - 1)} \sum _{a,s} N S\left( \rho _{(a,s)} \right) \\&= N n \log (2) - N (n-1) \log (2) = N \log (2),\) 
